Charles
Allen and his brother Bill Allen have learned a lot about
geothermal energy. Here are some questions that students have sent to them.
Charles and Bill have lots of colleagues in the geothermal industry. If they
don't know
the answer to your question, they'll forward it to an expert for an answer!

Dear
Charles,
You're always talking about magma. So what is
it, where does it come from, why is it hot, and where can I go to see some?

Sincerely,
Amanda S.

Dear
Amanda,
Wow! Well, first, magma is melted rock. It's
made within the mantle--the layer of rock that lies just beneath the earth's
crust. That means it comes from 60 to 200 miles down. The rock keeps melting
because it's so hot down there.

And it stays hot! Sounds unbelievable but
itís true. The heat inside the earth is always being regenerated by breakdown
of radioactive elements. So the rock stays melted. The Earth's heat will always
be around. That's why geothermal energy is a renewable energy source.

You have seen hot magma if you have seen a
volcano erupt, maybe on TV. Lava is really the magma which is breaking right up
through the earth's crust.
Charles

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Dear
Bill,
Will we ever run out of geothermal energy?

Sincerely,
Nikki N.

Dear Nikki,
No. Future generations will always have
geothermal energy. Hydrothermal reservoirs contain both water (hydro) and heat
(thermal). The heat is always being generated deep in the earth. The water is
replenished by rainfall and by returning the used water back into the reservoir.
Bill

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Dear Charles,
If there is geothermal heat in the earth, why
don't my feet get hot?

Yours Truly,
Jordan M.

Dear Jordan,
They would if you put them in a hot spring,
but most places it gets hot slowly as you get deeper.

Geothermal energy is everywhere but mostly at
a safe depth.
Charles

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Dear
Bill,
If geothermal is so great, why don't we use
it to make all our electricity?

Louis A.

Dear Louis,
We would if we could. Making electricity
needs high temperature geothermal near the surface to be economical with present
day technology. So far, we only find high temperature geothermal in a few
places. Some other countries with fewer people and more volcanoes could get all
their electricity from geothermal resources.
Bill